The Effect of Material Composition on Dynamic Welding of Electrical Contacts

The dynamic welding behavior at make operation is one important characteristic of electrical contacts and a key parameter to ensure secure usage of electricity. Model switch and device tests have been performed to work out the main factors influencing contact sticking. The behavior of different silver metal oxides (Ag/CdO, Ag/SnO2, Ag/ZnO), including various groups of additives like low melting and boiling metal oxides (Bi2O3), high melting oxides (CuO, WO3), and combinations thereof were studied under different loads. Several working mechanisms - that significantly influence and define the sticking tendency - have been found for different arcing loads. They can be explained by metallurgical investigations and divided into mechanisms under low (below 0.3 Ws), medium (0.3 - 10 Ws), and high (above 10 Ws)arcing load. The paper presents a scientific basis to explain contact sticking failures under different types of loads and can be seen as a guideline for appropriate contact material selection.